1. Field
One or more embodiments relate to an inorganic electroluminescent (“EL”) device and a method of manufacturing the same.
2. Description of the Related Art
Inorganic electroluminescent (“EL”) devices are used as lamp-type light sources in cellular phone keypads, advertisement plates, medical equipment and the like. FIG. 1 is a schematic cross-section of a commercially available inorganic EL device. In the inorganic EL device of FIG. 1, a lower electrode 11 is formed on a substrate 10, a dielectric layer 12 is formed on the lower electrode 11, an inorganic emission layer 13 is formed on the dielectric layer 12 and an upper electrode 14 is formed on the inorganic emission layer 13. When a predetermined voltage is applied between the lower electrode 11 and the upper electrode 14 of the inorganic EL device, electrons are emitted from the dielectric layer 12 and accelerated by an electric field formed within the inorganic emission layer 13, and thus collide with phosphors included in the inorganic emission layer 13. Accordingly, red (“R”) visible light, green (“G”) visible light and blue (“B”) visible light are emitted from their respective phosphors, thereby forming an image. Although the inorganic EL is very thin, inexpensive and flexible, it provides low brightness, thus can have too little luminance for illumination of a display. However, there is a recent trend to increase the size of displays, such as a digital information displays (“DIDs”), home displays and the like. Therefore to facilitate application of inorganic EL devices to displays, including large displays, an inorganic EL device with improved brightness is needed.
Japanese Publication Patent No. 2006-244768 discloses an EL device in which an EL layer, a transparent electrode layer and a transparent substrate are sequentially stacked, a light diffusion layer is formed between the transparent electrode layer and the transparent substrate and a reflection-prevention film is formed on the light diffusion layer, wherein the light diffusion layer diffuses light guided by the transparent electrode layer as a waveguide.
However, the EL device disclosed in Japanese Publication Patent No. 2006-244768 has a limit in improving brightness and fails to provide clear colors, this light efficiency can be degraded.